A high-throughput enhancer trap technique will be refined and subsequently exploited to systematically define hundreds of genes that are important in the retinal development of zebrafish. The technique is a powerful adaptation of well-characterized P-transposon methods that have been so effective in dissecting the genetics of Drosophila development. In this case, the method relies on the selective expression of transposons tagged with a nontoxic fluorochrome, i.e., green fluorescent protein (GFP). Relatively efficient integration of the transposon has been demonstrated, and more than 5 percent of integration events are expected to lead to GFP expression under the control of endogenous enhancers in select populations of cells and tissues. Lines of fish in which GFP is expressed selectively in retina or other tissues will be identified and preserved for more detailed developmental, morphometric and genetic analyses by the principal investigator and others. As in Drosophila, a significant fraction of transposition events is expected to disturb normal gene expression and to lead to mutations or quantitative variants. This feature of the enhancer trap is particularly significant because it should enable a fine-grained analysis of subtle abnormalities in retina that would otherwise escape detection.